BestTong 12V-50V 30A DC Motor Speed Controller PWM Variable Speed Regulator Governor Switch with Ajustable Potentiometer Its own power supply reverse polarity protection, control voltage over-voltage protection Knob is with switch function, can control motor speed to change from 0 percent to 100 percent , and it is noise free when motor is at low speed 4 power tubes, 30A ceramic fuse, potentiometer jack between GND and 0-5v can be connected with PLC analog speed regulation High-efficiency, large torque governor can control the motor speed, small heat, has been repeatedly revised, has been widely stable applications in industrial PWM frequency: 12KHZ; Note: NOT for DC brushless motors